The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Lead acid batteries (LABs) are the single largest class of batteries used today. They are essential for applications ranging from starting automobile engines, providing emergency back-up power for data centers, and powering industrial and recreational vehicles such as fork lift trucks and golf carts. Unlike any other battery type, LABs are almost 100% recycled rendering lead the single most recycled commodity.
Notably, all or almost all of the current commercial lead recycling from LABs is still based on lead smelting, which is a pyro-metallurgical process in which lead, lead oxides, and other lead compounds are heated to about 1600° F. and mixed with various reducing agents to remove oxides, sulfates, and other non-lead materials. Unfortunately, current lead smelting is a highly polluting process, generating significant airborne waste (e.g., lead dust, CO2, arsenic. SO2), solid waste (e.g., lead containing slag), and substantial amounts of liquid waste (e.g., lead contaminated sulfuric acid, arsenic salts), and continual pollution issues have forced the closure of many smelters in the US and other Western countries. Still further, lead smelting operations produce lead in bulk form, typically as ingots, which require significant processing to transform the ingots into other form factors. Moreover, where production of lead alloys or composite materials is desired, ingots need to be re-melted and mixed with another element or component.
To circumvent issues associated with smelting operations, lead can be electrolytically recovered from solution in various acid based processes. For example, U.S. Pat. No. 4,927,510 teaches a recycling process in which desulfated battery paste is treated with fluoboric or fluosilicic acid to form an electrolyte from which lead is plated onto a cathode. However, the fluoboric or fluosilicic acid are highly aggressive solvents and are environmentally problematic. To help circumvent such problems. MSA (methane sulfonic acid) can be employed as a lead bearing electrolyte as described in WO2014/076547. Here, lead is plated from MSA at the cathode as a thick deposit. Similarly, U.S. Pat. No. 7,368,043 teaches an acidic electrolytic lead recovery process in which lead is plated from relatively low lead concentrations as a thick film on a cathode of a dedicated electrolytic flow-through cell. Unfortunately, these acidic electrolytic processes lead to deposition of metallic lead in a film that is difficult to remove. In addition, and once removed, the lead films require yet again significant efforts to convert the recovered metallic lead into suitable form factors, and will require re-melting for alloy or composite material production. Moreover, as is not uncommon in electrowinning, power outages during plating will lead to re-dissolution of the plated lead back into the electrolyte, which adversely affects economics of the process.
All publications and patent applications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Electrochemical recovery of metallic lead can also be performed from substantially neutral solutions (pH 6-7) as described in U.S. Pat. No. 8,409,421. Here, lead is carried in an ammonium chloride containing electrolyte and passed through a flow-through electrochemical cell that produces non-adherent metallic sponge lead entrained in the electrolyte. However, while the process is generally environmentally benign and produces metallic lead that is not deposited in a sheet, the process consumes various reagents, runs at elevated temperatures, is relatively complex, and therefore economically less attractive. Moreover, so produced metallic sponge lead is relatively coarse, can clog the electrochemical flow-through reactor and is susceptible to oxidation throughout the process. In addition, residual electrolyte will include ammonium chloride, which may interfere with various downstream uses of the metallic lead product. For example, residual ammonium chloride reacts with lead salts to form fulminating compounds.
In still further known solution-based lead recovery processes, lead is recovered from an alkaline solution at a cathode as scarcely adherent spongy lead having relatively small particle sizes (about 20 micron) as described in U.S. Pat. No. 4,107,007. Notably, the lead was reported to float on the electrolyte when formed in an electrolyte with certain additives. However, the '007 process requires significant quantities of such additives, and especially polyol additives to increase the solubility of the lead compounds and to influence the form of the precipitate of the galvanically deposited and precipitated lead. Unfortunately, while the so produced lead has a relatively small particle size, the lead quality is poor as reported in U.S. Pat. No. 8,409,421, likely due to the presence of the additives. Thus, lead products from so produced processes fail to have a required purity.
Consequently, even though numerous processes are known in the art to produce lead in a metallic form from an electrochemical process, all or almost all of them fail to produce sufficiently pure lead. Moreover, and especially where the lead was produced as a relatively fine grained material, the so produced lead is subject to passivation/oxidation, and may also include additives that are detrimental to downstream processing. Still further, none of the know lead compositions were reported suitable for use in cold forming of various structures, let alone in cold forming of various alloys. Therefore, there is still a need for improved lead compositions and methods therefor.